Drops phenobarbital

Another patient taking phenobarbital, phenytoin and carbamazepine was foimd to have an imchanged phenobarbital level 2 days after switching from an antiretroviral regimen including indinavir to one containing ritonavir 300 mg twice daily and saquinavir. His plasma levels of car-bamazepine , (p.810), had doubled, and there was a 32.7% drop in the levels of phenytoin , (p.812). 

An HIV-positive man taking phenytoin and phenobarbital for epilepsy had been taking nelflnavir 750 mg three times daily and stavudine 30 mg twice daily for nearly 3 months when he had a tonic-clonic seizure. After starting nelflnavir and stavudine, serum phenytoin levels were found to have dropped from around 10 mg/L to around 5 mgfL Similarly, nelflnavir 1.25 g twice daily for 7 days decreased the AUC of phenytoin by about 30% and the maximum serum level by 21%, in healthy subjects, whereas the nelflnavir levels were not altered. ... 

---